It is well-established that African Americans experience more clinical pain than non-Hispanic Whites. However, the reasons for this discrepancy in clinical pain are not known. Therefore, the purpose of this project is to investigate ethnic differences in stress responsive pain regulatory mechanisms and psychosocial stress, both of which may be related to ethnic differences in clinical pain prevalence and severity. Specifically, ethnic differences in temporal summation of heat pain, which may be indicative of central sensitization in pain pathways, the relationships involving stress-responsive biological measures and pain sensitivity, as well as psychosocial stress (socio-economic-status and discrimination stress), all known to predict pain clinical pain will be examined. A sample of 88 medically healthy individuals (50% African American, 50% non-Hispanic White; 50% Women in each ethnic group) will be recruited to participate. Individuals will report to the lab for a single testing session, during which the participants will complete psychosocial questionnaires to assess stress. The subjects will undergo testing for pain tolerance to cold pressor pain and the temporal summation procedure, which involves the delivery of 10 heat pulses at 52[unreadable]C. The increase in pain perception to the temporal summation procedure is centrally mediated, and it is predicted that African Americans will report a greater pain intensity rating at each trial and will have a greater drop-out rate. Blood pressure and plasma norepinephrine, cortisol, and beta-endorphin levels will then be measured at baseline rest and in response to the Trier Social Stress Test. It is predicted that greater psychosocial stress in African Americans will be associated with a blunted blood pressure and neuroendocrine response to stress and with the absence of predicted relationships involving stress- responsive biological factors and pain sensitivity. The results of this study are expected to provide insight into biobehavioral and psychosocial stress factors that may contribute to ethnic disparities in clinical pain. [unreadable] [unreadable] [unreadable]